1. Field of the Disclosure
The present disclosure relates generally to wireless charging, and more particularly, to a method for determining a cross connection during wireless charging.
2. Description of the Related Art
Wireless charging is based on wireless power transmission and reception. For example, when a portable phone is placed on a charging pad, without being connected to an additional charging connector, a battery in the portable phone is charged.
Wireless charging offers benefits of increased waterproofing due to the removal of a charging port and enhanced portability due to the elimination of carrying a wired charger for an electronic device.
There are three basic wireless charging schemes: (1) electromagnetic induction using coils, (2) resonance-based, and (3) Radio Frequency (RF)/microwave radiation, which is based on conversion of electric energy to microwaves.
The electromagnetic induction-based power transmission transfers power between primary and secondary coils. When a magnet moves through a coil, current is induced. Based on this principle, a transmitter creates a magnetic field and a receiver produces energy from current induced by a change in the magnetic field. This phenomenon is commonly referred to as “magnetic induction” and power transmission based on magnetic induction is highly efficient.
The resonance-based power transmission resonates electromagnetic waves carrying electric energy, instead of sound. The resonant electrical energy is directly transferred only to a device having the same resonant frequency, while the unused electric energy is reabsorbed into the electromagnetic field, rather than being dispersed in the air. Thus, the resonant electrical energy does not affect nearby machines or human bodies, compared to other electronic waves.
A wireless power transmitter and a wireless power receiver may communicate with each other based on a predetermined method, for example, a ZigBee scheme or a Bluetooth Low Energy (BLE) scheme. By using an out-band method such as ZigBee or BLE, an available distance of communication increases. Thus, even when the wireless power transmitter and the wireless power receiver have a relatively long distance therebetween, the transmitter and receiver may still communicate with each other. That is, even at distance in which the wireless power transmitter will have difficulty in transmitting wireless power, the wireless power transmitter may still be able to communicate with the wireless power receiver.
FIG. 1 illustrates a cross connection that occurs in conventional wireless charging systems.
Referring to FIG. 1, a first wireless power receiver RX1 is disposed on a first wireless power transmitter TX1 and a second wireless power receiver RX2 is disposed on a second wireless power transmitter TX2. Herein, the first wireless power transmitter TX1 transmits power to the first wireless power receiver RX1 and the second wireless power transmitter TX2 transmits power to the second wireless power receiver RX2. Thus, the first wireless power transmitter TX1 communicates with the first wireless power receiver RX1, and the second wireless power transmitter TX2 communicates with the second wireless power receiver RX2.
However, due to increased communication distances, the first wireless power receiver RX1 may also join a wireless power network controlled by the second wireless power transmitter TX2 and the second wireless power receiver RX2 may also join a wireless power network controlled by the first wireless power transmitter TX1, which is referred to as a “cross connection”. As a result, the first wireless power transmitter TX1 may transmit power requested by the second wireless power receiver RX2, instead of power requested by the first wireless power receiver RX1. For example, if a power capability of the second wireless power receiver RX2 is greater than that of the first wireless power receiver RX1, over-capability power may be applied to the first wireless power receiver RX1. Further, if the capability of the second wireless power receiver RX2 is less than that of the first wireless power receiver RX1, the first wireless power receiver RX1 may not receive enough power to efficiently charge the first wireless power receiver RX1.